It has become common practice in the field of surgery to perform complex, prolonged life-saving surgical procedures on the heart. These procedures may include maintaining the circulation of transplantation candidates and pumping for periods as long as several days by artificial means while a suitable donor heart is sought. Similarly, it is also common practice for the surgeon to manually stimulate the heart to pump. However, this can only be maintained for short time periods on the order of minutes, before the surgeon becomes fatigued.
In response to the above-noted need, alternative methods of pumping or assisting the heart to pump have been developed. For example, heart-lung machines have been developed which actually circulate the blood through a pump and are commonly used in procedures such as coronary artery bypass, valve repair, and transitioning to other blood pumps. The heart-lung machine is deficient as it is virtually impossible to circulate the blood through a pump without causing damage to the blood cells and blood born products which can result in post-surgical complications such as bleeding, thrombi formation, and an increased risk of infection.
In response to the above noted deficiencies, an effort was made to develop methods of pumping the heart which did not require direct contact between the pump and the blood. In general, these devices comprise a device which wraps all or a portion of the heart and applies a mechanical force that squeezes the heart in order to pump blood through it.
These devices have a number of features in common. They usually comprise an outer cup of generally parabolic shape and include a flexible inner membrane, also of a similar parabolic shape which is connected to the outer cup along its periphery so as to create an air space therebetween. The outer cup includes an air inlet/outlet and a vacuum pump is utilized to alternately impose a vacuum and to pressurize the air space. Thus, when the air space is pressurized, the membrane moves away from the outer wall and squeezes the heart, thus pumping blood and when the pressure is reversed, the heart is returned to the normal position, thus allowing blood to flow back into the heart to be pumped on the next cycle.
However, the ventricular actuation cups described above are also not without their inherent drawbacks and deficiencies, as most, if not all of the devices taught in the prior art patents fail to give adequate consideration to the basic fact that there is variability in the size and shape of the human heart. Thus, when these devices are used, they exhibit one or more of a number of deficiencies. For example, if the shape of the heart does not closely conform to the shape of the cup, the ventricles can become dislodged from the cup resulting in trauma to the heart muscle and inefficient pumping of the ventricle which is exacerbated the longer the cup is used. Also, if the lip, or flange, of the cup which maintains the seal is "constricting" or "too tight", this can result in trauma to the heart in areas of constriction. Similarly, prior art devices utilize inadequately controlled ventricular pumping pressures which do not adequately or reliably empty both chambers of the heart. This frequently results in inadequate blood flow from either ineffective left or right chamber pumping, or pulmonary edema caused by ineffective pumping of the left chamber or ventricle thereby allowing blood to accumulate in the lungs.
With the foregoing in mind, it is an object of the present invention to provide a heart massage apparatus that reliably and efficiently pumps the heart muscle.
Another object of the present invention is to provide a heart massage apparatus that effectively retains the heart within the cup.
Still another object of the present invention is to provide a heart massage apparatus that minimizes trauma to the heart muscle while it is being pumped.
Yet another object of the present invention is to provide a heart massage apparatus that substantially eliminates trapping of blood in the lower chambers of the heart or in the lungs.